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- Ahmad, Tashfeen
(författare)
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Diabetic osteopathy : a study in the rat
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present study on non-obese Goto-Kakizaki (GK) rats with type-2 diabetes and neuropathy was an attempt to describe and define pertinent features of diabetic osteopathy. Altogether, the study included 33 GK rats aged 12 and 20 months, and 36 age-matched Wistar rats as controls. All underwent test of glucose tolerance and nerve (sciatic) conduction velocity (NCV) showing that the diabetic rats had significantly higher blood glucose levels and lower NCV confirming the presence of diabetes and neuropathy. Skeletal features: Radiologic analysis of bone entailed X-ray, Dual Energy X-ray Absorptiometry (DEXA) and peripheral Quantitative Computed Tomography (pQCT). In diabetic rats, the length of humerus and height of vertebrae was reduced by 8%. The long bones exhibited endosteal erosion of the diaphyses up to 18% and periosteal expansion up to 8%. The vertebrae and metaphyses of long bones showed a decrease up to 24% in areal bone mineral density (BMD), whereas no decrease was seen in the diaphyses. Cross-sectional measurements by pQCT showed a decrease in volumetric BMD ranging from 33 to 62%, which exclusively pertained to trabecular bone (vertebrae, metaphyses), whereas volumetric BMD of the cortical bone of diaphyses was only marginally affected. The results indicate that juxta-articular bone in diabetes is substantially weaker, whereas diaphyseal cortical bone may be even stronger. Over all, the observations suggest that the diabetic skeleton is characterized by regional changes, which cannot be explained by systemic factors like calcium regulating hormones. Local bone turn-over is regulated by complex mechanisms involving cytokines, prostaglandins, growth factors and, also neuropeptides. Further analysis focused on the insulin-like growth factor (IGF) system and neuronal mediators in bone. IGF system: Immunoassays of IGF-I were done on serum, ankle samples and cortical preparations. In addition, the inhibitory IGF-I binding proteins, IGFBP-1 and -4 were analysed in serum. In diabetic rats, serum IGF-I was reduced by 18%, while IGFBP-1 and IGFBP-4 were increased by 89 and 20%, respectively. This complies with the lower BMD in the diabetic rats. In cortical bone, IGF-I was reduced by 38%, whereas no change was seen in ankles. The loss of IGF-I in cortical bone represents a novel finding. Given the cortical expansion observed in diabetic rats, the opposite was expected. Conceivably, loss of IGF-I results in endosteal erosion, which is compensated by periosteal expansion. Neuropeptides: The analyses focused on two sensory mediators, i.e. substance P (SP) and calcitonin gene- related peptide (CGRP), and one autonomic, i.e. neuropeptide Y (NPY). Immunohistochemistry was applied to ankles and tibial diaphyses, whereas radioimmunoassay (RIA) was used for separate preparations of periosteum, cortex and bone marrow from femur and tibia, whole ankles, dorsal root ganglia (DRG) and lumbar spinal cord. The morphological analysis showed SP, CGRP and NPY positive nerve fibers in bone and joints, which mostly were blood vessel related, although free terminals were also seen. In addition, NPY-positive hematopoietic cells were observed in the bone marrow. RIA revealed a significant decrease of CGRP, albeit not of SP, in DRG (-26%) and spinal cord (-29%) in the diabetic rats. As for bone, only NPY was significantly reduced, most evidently in bone marrow (-66%), but also in cortical bone (-36%) and ankles (-29%). Given the bone anabolic effects of CGRP and NPY, loss of these neuropeptides may prove, at least partly, to underlie the trabecular osteopenia and endocortical erosion observed in diabetic rats. Conclusion: The skeleton of diabetic rats with type-2 diabetes and neuropathy is characterized by regional changes of size, form, mineral content and density and concomitantly with regional abnormalities of the IGF- system and neuropeptides suggesting that also local factors beyond systemic play an important role in the development of diabetic osteopathy.
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| 2. |
- Ahmad, T., et al.
(författare)
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Frequency and outcomes of undiagnosed diabetes mellitus in patients presenting with acute myocardial infarction
- 2020
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Ingår i: Medical Forum Monthly. - : Medical Forum Monthly. - 1029-385X. ; 31:12, s. 3-7
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To find out frequency and outcomes of undiagnosed diabetes mellitus in patients presenting with acute ST elevation myocardial infarction (STEMI). Study Design: Descriptive / Cross-Sectional Study Place and Duration of study: This study was conducted at the Cardiology Department, Lady Reading Hospital, Peshawar from November 2018 to May 2019. Materials and Methods: Patient of either gender having age ranging between 30-75 years old with acute STEMI who present within 12 hours of symptoms and with no past history of documented diabetes mellitus were included in the study. Venous blood samples for laboratory data, including random blood sugar, two fasting blood sugar and HBA1c using hitachi modular evo p800 machine was done. Results: A total of 158 patients having acute STEMI were studied. Males were 68.4% (n=108).The mean age was 59.65 ±10.80 years. Frequency of undiagnosed diabetes mellitus was 31.64 % (n = 50). In non-diabetics stress hyperglycemia was found in 51.85 % (n=56) patients. Among various types of STEMI, anterior STEMI was more common presentation 34.1 % (n=54. p= 0.85). Mean HBA1C was 6.19 ± 1.87%. Frequency of Ventricular tachycardia (VT) was 22.2 % in which undiagnosed diabetics were n=18 (p=0.004).Ventricular fibrillation was present in 13.3 % patients with undiagnosed diabetics were n=14 (p=0.001). Frequency of AF was 13.9% (n=22) with undiagnosed diabetics having AF in n=13 (p=0.003). SVT was present in 5.7% (n=9) patients with not significant difference between two groups (p=0.017). Among various mechanical complications VSR was present in 10 % (n=16) of patients (p=0.001), cardiogenic shock in 11.1 % (n=18) patients (p=0.004), acute LVF was present in 15.8 % patients (p=0.017). Conclusion: In our study we concluded that one third of patients having acute ST elevation myocardial infarction have undiagnosed diabetes mellitus (31.64 %, n = 50). The most common complication was ventricular tachycardia among electrical complication and LVF among mechanical complication.
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| 3. |
- Ahmad, Tauseef, 1986, et al.
(författare)
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Methodology for Power-Aware Coherent Receiver Design
- 2013
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Ingår i: Optics InfoBase Conference Papers. - 2162-2701. ; , s. SPT4D.4-
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Konferensbidrag (refereegranskat)abstract
- We describe a methodology to design and evaluate DSP hardware for a coherent receiver. Important parameters that can be assessed include DSP power consumption and chip area.
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| 5. |
- Ridella, Stephen, 1959
(författare)
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The Contribution of Vehicle, Occupant and Crash Factors to the Risk of Injury as a Result of Vehicle Rollover - New approaches to data and modeling analysis
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Injuries and deaths as a result of vehicle rollover remain a consistently large contributor of the overall crash fatalities in the United States. While more new vehicles are becoming equipped with electronic stability control and rollover ejection countermeasures as well as increased roof strength, it will take several years of production before these newer vehicles permeate the fleet and the effectiveness of these technologies can be fully assessed. In the interim, continued vigilance on assessment of rollover injury causation is recommended. This can be done through systematic analysis of aggregate field crash data and specific case studies. Also, mathematical modeling studies can be done to assess the contributions of vehicle, occupant and crash factors to the injury risk of rollover involved occupants. The major aims of the research in this thesis are to determine how rollover crash investigations and crash field data analysis can determine the most frequent types of injuries and their mechanisms that occur to belted, unejected occupants involved in rollover crashes and, once determined, identify the role of vehicle, occupant and crash factors that can predict injury risk. The first aim can be achieved through case studies and aggregate national crash data analysis while the second aim uses finite element and multi-body modeling of rollover crashes. Aggregate rollover field data was taken from the National Automotive Sampling System – Crashworthiness Data System (NASS-CDS). Head, spine (cervical) and thoracic injuries dominated the injury with specific injury types in each body region indicating areas of further interest to investigate regarding injury causation. Analysis of specific case studies taken from the Crash Injury Research Engineering Network (CIREN) indicated that single event, single vehicle (pure) rollovers were associated with complex mechanisms of cervical spine injuries that were associated with vehicle roof strength (strength to weight ratio), and the amount of vertical as well as lateral intrusion at the injured occupant location. Occupant body mass index was a possible contributor to injury risk. A finite element model of a contemporary sedan was used in a simulation of a Controlled Rollover Impact System (CRIS) test to identify vehicle and crash parameters that were most associated with high cervical neck forces in the Hybrid III dummy occupant model. The variables that contributed the most to the occupant and vehicle structural response were pitch angle, roll angle, and drop height. These factors determine where and with what force the vehicle roof impacts the ground. The analysis showed that proper selection of a crash dummy model is also a critical step in the interpretation of effects of the factors used in analysis. Subsequent MADYMO modeling of the CRIS test with the models of the Hybrid III and THOR advanced frontal crash dummy and a facet model of the human body were performed with imported finite element nodal vehicle model outputs representing vehicles with the strongest and weakest roof. When coupled with a parameter analysis of advanced vehicle seat belt restraints, the analysis showed that stronger roofs will reduce injury risk, and that restraint systems can provide additional protection to reduce the potential for occupant head impact to the roof. The analysis approach to both data and modeling in this thesis provided results through innovative combined crash field data analysis, parametric computer modeling methods and statistical and human body modeling techniques to arrive at the conclusions reached. As future vehicle design evolves with respect to automation and other propulsion systems, designers and engineers need to be aware of the iv structural and occupant restraint requirements these vehicles will need as they interact with the fleet and are exposed to potential rollover situations.
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| 7. |
- Corander, Jukka, 1971-
(författare)
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On Bayesian graphical model determination
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A graphical model specifies a graph representation of the independence structure of a multivariate distribution, where nodes represent variables and edges association between variables.This thesis introduces methodology for determination of graphical models for multivariate distributions within the exponential family. Model determination is understood in the present context as quantification of the uncertainty about the association structure, given empirical observations. Only models with symmetric associations between variables are considered. The distributions investigated are multinomial, multinormal and conditional Gaussian (CG) distributions. Local graphical models which generalize the graphical loglinear models for multinomial distributions are introduced. These models allow conditional associations to be absent locally, in parts of the sample space.A unifying theme is that the models are represented in terms of affine restrictions to the parameters of a regular exponential model. All introduced methods are applicable to the complete class of graphical models, consisting of both decomposable and non-decomposable models. Various real data sets investigated earlier in the graphical modeling literature are used to illustrate the methods.Two different measures of model uncertainty are considered: the posterior probability and the relative expected utility of a model. Posterior probabilities are estimated by a Markov chain Monte Carlo sampling method. The other measure of model uncertainty is derived in a decision theoretic framework under reference priors for the model parameters.The expected logarithmic utility of a model is decomposed into predictive performance and relative cost. The predictive performance is measured by posterior expectation of the negative entropy of the distribution induced by a graphical model. This expectation has an analytic expression for decomposable models, while a simulation consistent estimate can be obtained for non-decomposable models. The expected logarithmic utility is asymptotically equivalent to the Schwarz criterion under a certain cost function.
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| 9. |
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| 10. |
- Kobyakov, D., et al.
(författare)
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Nucleus-nucleus interactions in the inner crust of neutron stars
- 2016
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Ingår i: Physical Review C. - : American Physical Society. - 2469-9985. ; 94:5
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between nuclei in the inner crust of neutron stars consists of two contributions: the so-called "direct" interaction and an "induced" one due to density changes in the neutron fluid. For large nuclear separations r the contributions from nuclear forces to each of these terms are shown to be nonzero. In the static limit they are equal in magnitude but have opposite signs and they cancel exactly. We analyze earlier results on effective interactions in light of this finding. We consider the properties of long-wavelength collective modes and, in particular, calculate the degree of mixing between the lattice phonons and the phonons in the neutron superfluid. Using microscopic theory, we calculate the net non-Coulombic contribution to the nucleus-nucleus interaction and show that, for large r, the leading term is due to exchange of two phonons and varies as 1/r(7); it is an analog of the Casimir-Polder interaction between neutral atoms.
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